The present invention relates to a fluorescent X-ray film thickness measuring system.
In a known system used for this purpose, as shown in FIG. 6, samples are placed on a sample table 66. The operator moves the sample table to register the cross wires of a sample monitor unit 65 with the measurement desired location of the sample thereby to locate the position of measurement. In case the samples to be measured are thin, an observing optical system of low magnification is usually used to cover a wide range, but positioning with the aid of the sample monitor unit is then difficult. Thus, there has been adopted a switching system which can switch to an optical system of high magnification. Alternatively, the scanning is carried out in steps sufficiently smaller than the width of the samples so that the film thickness is determined from the measured result of the center of the samples, which is decided from the scanning profile.
Even the positioning of the prior art using the sample monitor unit could achieve a practical sufficiency for relatively large samples. As the miniaturization of electronic parts proceeds in recent years, however, precise positioning based on images on the sample monitor unit has become difficult because of limits on the resolution of the images and on the precision in the adjustment between the position to be irradiated with X-rays and the position of the cross wires of the sample monitor unit. In case, moreover, automatic measurements are to be continuously effected by registering the measurement position in advance, the allowance for the movement of a sample, if any, when the sample stage is operated, is seriously restricted to enhance the necessity for the function to effect the precise positioning.
For samples whose centers are difficult to position by an optical system of low magnification, on the other hand, the method of switching to an optical system of high magnification has the drawback that the system becomes expensive, and the method of determining the center from the profile takes a long time to measure the film thickness of one point, so that such an arrangement is not practical.